Shelf unit



FIG. 1 is a front perspective view of our new design for a shelf unit;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is an enlarged top view thereof;

FIG. 4 is a front side view of FIG. 3;

FIG. 5 is a left side view of FIG. 3;

FIG. 6 is a right side view of FIG. 3;

FIG. 7 is a rear view of FIG. 3; and,

FIG. 8 is a bottom view of FIG. 3. 

The ornamental design for a shelf unit, as shown. 